Typically, contents published on the Internet or the like, such as web pages, include a plurality of images and text and are made of hypertext markup language (HTML) files in which source data for displaying the images and text is described. One example method of determining whether such an HTML file is correctly displayed on a browser is an automatic syntax check on source data of html files. Another checking method is visual verification by actually displaying web pages using html files on a browser and visually testing them by an operator or a person who handles test.
A method of checking syntax of source data of an HTML file detects a syntax error of source data. With this check method, even if there is no syntax error, an HTML file that would be poorly displayed when being actually displayed may be unable to be found.
In this case, such an HTML file is detectable using visual verification by displaying it on a screen through a browser and testing it. In renewing an enormous number of web pages forming a web site, newly creating all web pages from scratch is rare. For such a renewal, new web pages (HTML files) are often created by automatic conversion based on a large number of existing HTML files using a conversion tool.
Unfortunately, even in this case, an operator must inspect displaying through a browser after automatic conversion of a large number of web pages using a tool. 1f the number of pages to be tested reaches tens of thousands, for example, human visual verification needs much time and effort in checking all pages. Such a visual verification task has a problem because repeated simple large-volume operations for many hours typically reduce working efficiency and cause human fatigue and this may induce an operator to make a mistake.